It is well established that youth offenders suffer mental health and substance abuse disorders at disproportionately high rates when compared to youth in the community without any history of justice system involvement. In efforts to rehabilitate delinquent youth and prevent criminal recidivism, policymakers and researchers have developed and implemented evidence-based behavioral health treatments specific to offenders. However, the research literature has rarely confirmed that such services actually reduce criminal recidivism among adolescent offenders, especially when services for a range of behavioral health needs are considered. Previous studies, moreover, have not quantified the frequency, duration, and type of behavioral health service utilization most likely to improve delinquency-related outcomes. Therefore, the primary objective of this project is to assess whether adequate episodes of behavioral health treatment reduce criminal recidivism among a large population of adolescent offenders. To accomplish our objective, our interdisciplinary research team will prepare and analyze the justice system and electronic health records (EHR) of more than 150,000 youth from Marion County (Indianapolis), Indiana. The resulting 15-year retrospective, longitudinal analytic database will include youth with a wide array of experiences in both the behavioral health and criminal justice systems. We expect that more than one third of sampled youth will have a juvenile criminal record, including more than 40,000 youth with records from their first encounter with the justice system (i.e., first arrest). In this way, we will capture a variety of developmental stages, behavioral health diagnoses, criminal charges, and pathways through both the behavioral health and justice systems. We will create and to analyze a comparison group of community youth (i.e., non-offenders), in order to strengthen our understanding of adolescent behavioral health utilization patterns. By employing existing performance measures of treatment quality for adequate behavioral health treatment, we will highlight meaningful differences in service utilization between offenders and community youth, and within the group of offenders. We expect that differences in the timing and intensity of behavioral health care utilization among offenders will affect whether and how treatment reduces recidivism. Lastly, we will assess the role that delinquency case dispositions (i.e., conditions of probation) play in the relationship between behavioral health service utilization and criminal recidivism. Specific aims include: Aim 1. Compare the behavioral health treatment needs and behavioral health service utilization of youth offenders to those of community youth. Aim 2. Test the relationship between behavioral health service utilization and criminal recidivism among youth offenders. There is a substantial cost of juvenile criminal behavior to society. We expect to quantify if BH treatment reduces criminal recidivism. The long-term goal of this project is to identify specific points along the continuum of justice system involvement (e.g., arrest, detention, incarceration, and transfer to adult court) where utilization of behavioral health services will have the most impact in reducing criminal recidivism.